Complete automation of molded case circuit breaker components by robotic assembly have not heretofore been completely successful. One impediment to complete robotic assembly is the attachment of a flexible conductive braid between the circuit breaker contact carrier and the circuit breaker trip unit or load terminal lug.
Early attempts to eliminate the electrical contact braid are found in U.S. Pat. Nos. 3,023,292, 3,033,964 and 3,073,936 wherein a pair of contact carriers are supported on a contact arm carrier support by means of a pivot pin and a thick spring clip is fastened to the carrier support and arranged around both the contact carriers and the carrier support. Direct electrical connection between the spring clip and the terminal conductor in some higher current industrial rated circuit breaker designs advantageously improves the electrical conduction between the terminal conductor and the movable contact arm by the electromagnetic forces of attraction generated by the current through the spring clip. The increasing electric current increases the electromagnetic force on the juncture between the movable contact arm and the terminal conductor to create an increasing compressive force therebetween. In other designs, such as required in certain lower current rated current limiting industrial circuit breaker designs, the forces exerted by the spring clip on the movable contact arm and the terminal conductor must remain relatively constant with increasing current to ensure that the contacts can be electrodynamically repulsed and separated under high current faults such as those occurring with short circuits. The contact arm must rapidly move about its pivot in the early stages of the current waveform to separate the contacts with minimum let-through current at the instant of separation. This is not easily obtained when the compressive forces on the movable contact arm and the terminal conductor substantially increase at the time the movable contact arm is required to rotate about its pivot.
U.S. Pat. Nos. 4,240,053 and 4,554,427 each disclose a circular segment formed within the movable contact carrier and are arranged over a circular segment formed on the terminal conductor to form a conductive junction between the contact carrier and the terminal conductor.
U.S. Pat. No. 4,160,142 utilizes a pair of washers, a nut and a bolt to connect the movable contact carrier to the terminal conductor to electrically connect the contact carrier with the terminal conductor.
U.S. Pat. No. 4,245,203 discloses a clinch type electrical connection between the movable contact arm and a bifurcated pair of upright posts. Clamping force upon the contact arm pivot is provided by the resilience of the posts and by a bias spring clip.